Endocrinology, Vol 122, 3002-3004, Copyright © 1988 by Endocrine Society
Striated muscle fibers differentiate in primary cultures of adult anterior pituitary cells
O Spira, R Atzmon, E Rahamim, R Bar-Shavit, J Gross, A Gordon and I Vlodavsky
Hubert H. Humphrey Center for Experimental Medicine and Cancer Research, Jerusalem, Israel.
Anterior pituitary cells from adult male rats were cultured on a natural
extracellular matrix (ECM). From the 5th day, spindle-shaped cells, fusing
to form elongated fibers, were observed among the epithelial cells. These
fibers later increased in size and number and were identified as striated
muscle fibers, based on their multi- nucleation, cross-striation and
rhythmic contraction. Striated muscle development was further validated by
the appearance of cholinergic- nicotinic receptors, as demonstrated by the
binding of 125I-alpha bungarotoxin (a-Btx). The effect of various
supplements added to the cultures on a-Btx binding was used as a measure of
muscle cell differentiation. ECM and serum were essential for myotube
formation. Insulin (or IGF-I) and cortisol synergistically caused a 20-fold
increase in myogenesis. FGF and EGF were effective only in the presence of
insulin and cortisol. The data suggest that: (a) cells, derived from adult
pituitary, differentiate, in primary culture, into striated muscle fibers;
(b) the induction of this differentiation is multi- factorial; ECM, serum,
insulin and glucocorticoids facilitate this myogenesis.
